Design optimization of gate-all-around vertical nanowire transistors for future memory applications

This paper investigates the application of gate-all-around (GAA) vertical nanowire transistors (VNWFET) as an access element in future non-volatile memories (NVM) such as resistive random-access memory (RRAM), phase-change random access memory (PCRAM) and spin-torque-transfer memory (STT-RAM or MRAM). We primarily choose direct-current (DC) parameters I_ON and I_ON/I_OFF as our figure of merit (FOM) and optimize the vertical nanowire FET by taking various critical process parameters into account such as channel length, fin doping, gate overlap, and cross-sectional shape of the nanowire transistor. Further, using the optimized device in a 3×3 cross-bar array arrangement, we evaluate the read/write disturb due to the active device on it´s neighboring inactive devices. We show that the optimized access device can be used for a range of currents ratings required by different memory devices, I_ON being as high as 0.19 A/μm² and I_OFF being as low as 2 nA/μm².